Ariamalar Selvakumar

A watershed-scale design optimization model for stormwater best management practices

U.S. Environmental Protection Agency developed a decision-support system, System for Urban Stormwater Treatment and Analysis Integration (SUSTAIN), to evaluate alternative plans for stormwater quality management and flow abatement techniques in urban and developing areas. SUSTAIN provides a public domain tool capable of evaluating the optimal location, type, and cost of stormwater best management practices (BMPs) needed to meet water quality and quantity goals. It is a tool designed to provide critically needed support to watershed practitioners in evaluating stormwater management options based on effectiveness and cost to meet their existing program needs. SUSTAIN is intended for users who have a fundamental understanding of watershed and BMP modeling processes. How SUSTAIN is setup described here using a case study, conducted by actual data from an existing urban watershed. The developed SUSTAIN model was calibrated by observed rainfall and flow data, representing the existing conditions. The SUSTAIN model developed two BMP cost-effectiveness curves for flow volume and pollutant load reductions. A sensitivity analysis was also conducted by varying important BMP implementation specifications.

Particle-associated microorganisms in stormwater runoff

This research investigated the effects of blending and chemical addition before analysis of the concentration of microorganisms in stormwater runoff from a single summer storm to determine whether clumped or particle-associated organisms play a significant role. The standard membrane filtration method was used to enumerate the microorganisms. All organisms, except for Escherichia coli, showed an increase in the measured concentration after blending samples at 22,000 rpm with or without the chemical mixture. Other than fecal streptococci, the organism concentrations decreased with the addition of the Campers solution in both blended and unblended samples before analyses. There was a statistically significant interaction between the effects of Campers solution and the effects of blending for all the organisms tested, except for total coliform. Blending did not alter the mean particle size significantly. The results show no correlation between increased total coliform, fecal coliform, and fecal streptococcus concentrations and the mean particle size.

Wastewater collection system infrastructure research needs in the USA

Many of the wastewater collection systems in the USA were developed in the early part of the last century. Maintenance, retrofits, and rehabilitations since then have resulted in patchwork systems consisting of technologies from different eras. More advanced and cost-effective methods to properly rehabilitate these systems must be considered to guarantee sustainability into the future. Achieving sustainable development presents a challenge to deliver new and innovative infrastructure and facilities needed to serve society while protecting the environment. In the context of this paper, sustainable development would provide new and improved solutions to existing and emerging problems associated with wastewater collection system infrastructure. Such solutions would, for example, include consideration of innovative approaches and practices for identifying and rehabilitating problems in existing systems and ways of preventing these problems in new construction. The paper focuses on technical issues and research needs in three major areas: (1) assessment of system integrity; (2) operation, maintenance, and rehabilitation; and (3) new construction. Many of the issues and needs discussed were identified at a USEPA sponsored experts workshop on infrastructure problems associated with wastewater collection systems.

Role of Stream Restoration on Improving Benthic Macroinvertebrates and In-Stream Water Quality in an Urban Watershed: Case Study

Many stream restoration projects do not include a requirement for long-term monitoring after the project has been completed, resulting in a lack of information about the success or failure of certain restoration techniques. The National Risk Management Research Laboratory, part of the U.S. EPA Office of Research and Development, evaluated the effectiveness of stream bank and channel restoration as a means of improving in-stream water quality and biological habitat in Accotink Creek, Fairfax City, Va., using discrete sampling and continuous monitoring techniques before and after restoration. This project monitored the effects of a 549 m (1,800 linear-ft) restoration of degraded stream channel in the North Fork of Accotink Creek. Restoration, which was intended to restore the stream channel to a stable condition, thereby reducing stream bank erosion and sediment loads in the stream, included installation of native plant materials along the stream and bioengineering structures to stabilize the stream channel and bank. Results of sampling and monitoring for 2 years after restoration indicated a slight improvement in biological quality for macroinvertebrate indices such as Virginia Stream Condition Index, Hilsenhoff Biotic Index, and Ephemeroptera, Plecoptera, Trichoptera taxa; the differences were statistically significant at 90% level of confidence with the power of greater than 0.8. However, indices were all below the impairment level, indicating poor water quality conditions. No statistically significant differences in chemical constituents and bacteriological indicator organisms were found before and after restoration as well as upstream and downstream of the restoration. The results indicated that stream restoration alone had little effect in improving the conditions of in-stream water quality and biological habitat, though it has lessened further degradation of stream banks in critical areas where the properties were at risk. Control of storm-water flows by placing best management practices in the watershed might reduce and delay discharge to the stream and may ultimately improve habitat and water quality conditions.

Rehabilitation of Aging Water Infrastructure Systems: Key Challenges and Issues

AbstractPresented in this paper are the results of a state-of-the-practice survey on the rehabilitation of water distribution and wastewater collection systems. The survey identified several needs, including the need for rational and common design approaches for rehabilitation systems, quality assurance/quality control procedures and acceptance testing during installation of rehabilitation systems, and decision support tools for choosing rehabilitation/rehabilitation systems versus replacement. Discussed are separate issues for water and wastewater systems in terms of drivers for increased rehabilitation efforts and problems typically encountered. Also examined are the major technologies currently in use and the major issues and key challenges faced in terms of speeding rehabilitation efforts and documenting/improving the performance of the technologies used.

Quality assurance and quality control practices for rehabilitation of sewer and water mains

As part of the US Environmental Protection Agency (EPA)s Aging Water Infrastructure Research Program, several areas of research are being pursued including a review of quality assurance and quality control (QA/QC) practices and acceptance testing during the installation of rehabilitation systems (USEPA 2011). The objectives of this research effort were to collect, analyze and summarize information on the installation and QA/QC practices for the trenchless rehabilitation of sewer and water transmission mains. In addition, consideration was given to practices related to water service lines, sewer service laterals, force mains, siphons, sewer manholes, pumping stations, associated wet wells and other appurtenances. This review was accomplished primarily by conducting interviews directly with rehabilitation technology vendors, design engineers and water and wastewater utilities that have a track record of using trenchless rehabilitation technologies within their network. This paper provides an overview of how QA/QC issues have been handled in North America for trenchless rehabilitation technologies.

Evaluating the accotink creek restoration project for improving water quality, in-stream habitat, and bank stability

Increased urbanization results in a larger percentage of connected impervious areas and can contribute large quantities of stormwater runoff and significant quantities of debris and pollutants (e.g., litter, oils, microorganisms, sediments, nutrients, organic matter, and heavy metals) to receiving waters. To improve water quality in urban and suburban areas, watershed managers often incorporate best management practices (BMPs) to reduce the quantity of runoff as well as to minimize pollutants and other stressors contained in stormwater runoff. It is well known that land-use practices directly impact urban streams. Stream flows in urbanized watersheds increase in magnitude as a function of impervious area and can result in degradation of the natural stream channel morphology affecting the physical, chemical, and biological integrity of the stream. Stream bank erosion, which also increases with increased stream flows, can lead to bank instability, property loss, infrastructure damage, and increased sediment loading to the stream. Increased sediment loads may lead to water quality degradation downstream and have negative impacts on fish, benthic invertebrates, and other aquatic life. Accotink Creek is in the greater Chesapeake Bay and Potomac watersheds, which have strict sediment criteria. The USEPA (United States Environmental Protection Agency) and USGS (United States Geological Survey) are investigating

Exfiltration in sanitary sewer systems in the US

Many municipalities throughout the US have sewer systems (separate and combined) that may experience exfiltration of untreated wastewater. A study was conducted by the US Environmental Protection Agency (USEPA) to focus on estimating the magnitude of leakage of sanitary and industrial wastewater from sewer pipes on a national basis. The method for estimating exfiltration amounts utilized groundwater table information to identify areas of the country where the hydraulic gradients of the wastewater are typically positive, i.e. the wastewater flow surface (within pipelines) is above the groundwater table. An examination of groundwater table elevations on a national basis reveals that the contiguous US comprises groundwater regions (established by the US Geological Survey) that are markedly different. Many parts of the northeastern, southeastern, and midwestern US have groundwater tables that are higher than the wastewater flow surface, resulting in inflow or infiltration. Conversely, the combination of a relatively low groundwater table and shallow sewer systems creates the potential for widespread exfiltration, a situation more commonly found in communities located in the western US.

Evaluation of Retention Pond and Constructed Wetland BMPs for Treating Particulate- Bound Heavy Metals in Urban Stormwater Runoff

The sources of heavy metals in urban stormwater runoff are numerous (e.g., highways, road surfaces, roofs) and the release of metals into the environment is governed by several complex mechanisms. Heavy metals in stormwater are associated with suspended particulate materials that vary from coarse (>75 µm) and fine particulates ( 20 µm); Mn was mostly soluble while Cu and Zn were primarily associated with fine particulates (10 – 1 µm) and in the dissolved fraction (<0.4 µm) in stormwater runoff. Also, the retention pond and cattail wetland mesocosms were effective in attenuating Cu, Zn, and Al. Preliminary results are also presented for the chemical fractionation of cattail wetland sediments.

Demonstration and Evaluation of State-of-the-Art Wastewater Collection Systems Condition Assessment Technologies

AbstractCondition assessment of wastewater collection systems is a vital part of a utility’s asset management program. Reliable information on pipe condition is needed to prioritize rehabilitation and replacement projects, given the current state of our nation’s infrastructure. Although inspections with conventional closed-circuit television (CCTV) have been the mainstay of pipeline condition assessment for decades, other technologies are now commercially available. Five of these innovative technologies were selected for field trials under the U.S. Environmental Protection Agency (USEPA) demonstration program: zoom camera, electroscanning, digital scanning, laser profiling, and sonar. The goal of the field demonstration was to evaluate the technical performance and cost of these technologies. The field demonstration was conducted in August 2010 and was hosted by the Kansas City, Missouri Water Services Department. The innovative technologies were compared to CCTV inspection. Each technology identified mai...